In recent years, from a viewpoint of prevention of global warming, power consumption reduction is required for home appliances. In particular, refrigerators take a greater portion in power consumption amount in ordinary homes and its reduction is indispensable. In order to reduce power consumption amount of refrigerators, high efficiency of a compressor and high performance of a thermal insulating material become important.
While conventionally polyurethane foam (hereinafter, referred to as PUF) had been employed as a thermal insulating material, recently a vacuum thermal insulating material having superior thermal insulating performance to PUF has come to be used in combination with PUF. Such vacuum thermal insulating material is used for cold heat equipment such as a thermal insulating container, a vehicle air-conditioner, and a water heater in addition to refrigerators.
A vacuum thermal insulator has a powder, a foam, a fiber material, or the like inserted as a core member into an enveloping member composed of an aluminum foil laminated film having a gas barrier property (air barrier properly) or the like, of which inferior is maintained at a degree of vacuum of several Pa.
Although as a core material of the vacuum thermal insulating material, powder such as silica, foam such as urethane, and fiber body such as glasses are available, the fiber body having the most superior thermal insulating performance becomes a mainstream nowadays.
There are inorganic fiber and organic filer for fiber body. There are glass fiber, carbon fiber and the like for inorganic fiber (refer to Patent Literatures 1, 4, and 6, for example). There are polystyrene fiber, polypropylene fiber, polylactate fiber, aramid fiber, LCP (liquid crystal polymer) fiber, polyethylene terephthalate fiber, polyester fiber, polyethylene fiber, cellulose fiber and the like for organic fiber (refer to Patent Literatures 2, 3, and 5, for example).